A polysiloxane is researched and developed for utilizing the polysiloxane as one member of an electronic device, particularly a solid state imaging device by taking advantage of high transparency and high heat resistance due to a Si—O bond. The incorporation of the polysiloxane into an electronic device is performed through a process of coating an arbitral substrate with the polysiloxane by a wet process such as a spin coating method, and thus it is essential to prepare the polysiloxane as a polysiloxane vanish. The polysiloxane after the film formation thereof is generally baked using an arbitral baking equipment.
By baking the polysiloxane, intramolecular and intermolecular Si—OH bonds are condensation-polymerized with each other and the polysiloxane is polymerized to a polymer to form a rigid film. However, in the case where the condensation-polymerization of the Si—OH bond is imperfect, when the polysiloxane is incorporated into an electronic device, particularly a solid state imaging device as one member thereof, Si—OH bonds remaining after an aging test at a high temperature of the electronic device in a post-process are condensation-polymerized again and by dehydration of the electronic device, degasification is caused, so that the reliability of the electronic device is remarkably impaired. Accordingly, for solving this problem, remaining Si—OH bonds are necessary to be digested.
Thus, conventionally, there have been known methods such as (1) adding a baking process at a high temperature and for a long period, and (2) accelerating the condensation-polymerization by adding a thermobase generator to a reaction system to bake the polysiloxane (see Patent Document 1). The addition of the thermobase generator utilizes such a property that Si—OH bonds of the polysiloxane easily cause the condensation-polymerization of each other under a basic condition, and is effective for digesting remaining Si—OH bonds. A hitherto-reported thermobase generator accelerates the condensation-polymerization during baking by adding a primary amine or a secondary amine that is a moiety developing basicity in a high activity state into the thermobase generator or by adding a tertiary amine into the thermobase generator. However, there has been known that on the contrary, the preservation stability of a polysiloxane vanish in a frozen state, in a refrigerated state, or at room temperature is poor.
On the other hand, it is generally known that an acidic range of around pH 4 is a stable range for the preservation stability of a polysiloxane vanish in which the condensation-polymerization cannot be caused and a hydrolysis cannot be progressed. Conventionally, for enhancing the preservation stability of a polysiloxane vanish in a reaction system to which a thermobase generator is added, it is necessary to adjust pH to around 4, and a method of further newly adding a derivative of a carboxylic acid such as oxalic acid and maleic acid to the reaction system or similar methods are used for this adjustment.
However, the addition of the thermobase generator is effective for digesting remaining Si—OH bonds, but conversely unpreferably impairs the preservation stability of a polysiloxane vanish.
Then, there is required a polysiloxane composition capable of forming a polysiloxane film in which Si—OH bonds are remarkably digested during film formation/baking while advantageously maintaining the preservation stability of a polysiloxane vanish. There are also disclosed curable resin compositions containing a polysiloxane and an organic crosslinker (Patent Documents 2 to 4).